Microair Avionics M760 Transceiver Installation & User Manual
M760Q Install & User Manual 01R12.doc Page 11 of 36 30
th
March 2010
3.5 MICROPHONE
The M760 can be operated with an Electret Insert or Amplified Dynamic microphone. These alternatives
cover most aviation headsets and hand microphones.
When the PTT is pressed both microphones are live. To reduce background noise, the M760 can be
installed with relays across the mic lines and the PTT line, to allow only one microphone at a time to
operate.
3.5.1 ELECTRET
Electret microphones are the most common microphone in use on aviation headsets. They are small in
size, and can have noise cancelling capability. It is important to wire the Electret microphone with the
correct polarity. The Electret will only work if the positive and negative are wired correctly.
Electrets are a high signal device, and do not normally require amplification. Some headset
manufacturers elect to use an amplifier to improve the Electret’s response, and to provide some noise
filtering.
3.5.2 DYNAMIC
Dynamic microphones are a low signal device. A dynamic microphone will not operate directly with an
M760 radio, because of the low signal produced.
For operators wanting to use a
dynamic microphone, a mic
amplifier must be used.
Microair recommends the
installation of the Microair
MD-01a amplifier. This amp is
compatible with 150-600 ohm
dynamic microphones.
Refer to the Microair Avionics
website www.microair.com.au
for further details on
microphone types, and wiring
configurations.
3.6 SPEAKER
Microair recommends using a speaker of 8 ohms
impedance, rated at a minimum of 5 watts. The
speaker is wired to the speaker line (pin 15). Do NOT
attempt to connect a speaker to the headphone line
(pin 14). Likewise do NOT attempt to connect the
headphones to the speaker line.
Microair recommends the SP01 Box Speaker. The
SP01 has a durable thick film plastic cone of 8 ohms,
and is rated at 5 watts. The SP01 is fitted with a
mounting bracket, and 1.5m of screened cable.
Check your speaker installation by ensuring the audio
is clear all the way up to full volume.
MD-01a
CONNECTOR (RADIO END)
CONNECTOR (MIC END)
CRIMP TERMINALS
MIC SIGNAL LINE
(7-9 VOLTS)
GROUND
LINES TO DYNAMIC MIC
OR MIC JACK
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